1. Field of Invention
The present invention relates to a polarizing illumination device for generating about one type of polarized light, and to a projection display device including this polarizing illumination device.
2. Description of Related Art
In a projection display device, an element, called a light valve, is used to modulate light according to image signals. In most cases, light valves using only one type of linearly polarized light, such as a transmission liquid crystal panel, or a reflective-type liquid crystal panel, are used. Such a projection display device using one type of linearly polarized light includes a polarizing conversion element array that converts unpolarized incident light emitted from a light source into one type of linearly polarized light (e.g., s-polarized light). FIGS. 1(a)-(b) are explanatory views of a polarizing conversion element array. As shown in FIG. 1(a), such a polarizing conversion element array 320 includes polarization separating films 331 for separating incident light into p-polarized light and s-polarized light, and reflecting films 332. On the light emitting surface of the polarizing conversion element array, .lambda./2 phase layers 381 are selectively formed to unite two separated polarized lights into one type of polarized light.
The incident surface of the polarizing conversion element array 320 is divided into effective incident areas EA.sub.0 and ineffective incident areas UA.sub.0. Light that is incident on the effective incident areas EA.sub.0 is finally converted into s-polarized light, emitted, and guided to a light valve that is not shown. In the example shown in FIGS. 1(a)-(b), it is assumed that the object to be modulated by the light valve is s-polarized light. In other words, light that is incident on the effective incident areas EA.sub.0 is converted into effective linearly polarized components that are to be modulated by the light valve. On the other hand, if light enters the ineffective incident areas UA.sub.0, this light is converted into p-polarized light, and emerges from the polarizing conversion element array 320. This p-polarized light is an ineffective linearly polarized light component that is absorbed by a polarizer disposed on the light incident side of the light valve, thereby generating heat. Since such heat generation deteriorates the light valve, it is preferable that effective linearly polarized light components be limited to the smallest possible amount. Accordingly, in order to minimize the emergence of unnecessary linearly polarized light (p-polarized light), light-shielding portions 316 are disposed to block light that is incident on the ineffective incident areas UA.sub.0.